In one known structure of a gas supply device for a fuel cell system, two injectors having different flow rates are arranged in parallel with each other to regulate the amounts of gas going through the respective injectors (for example, PTL1). In general, the large injector has the large stroke and the high flow rate of the gas but cannot be opened even at the relatively low upstream pressure. The small injector, on the other hand, has the small stroke and the low flow rate of the gas and can be opened even at the relatively high upstream pressure.